DE1720440B2 - Polyester and process for its manufacture - Google Patents

Description

COOR '

(D

wherein RO on the ring in para- or meta-position to COOR 'and R and R' have the abovementioned meaning, at an elevated temperature in liquid state or in the presence of a high-boiling solvent in an inert atmosphere and in The presence of a condensation catalyst is condensed at a temperature of at least 250 ° C.

4. The method according to claim 3, characterized in that the condensation is carried out in a polyaromatic ether as a solvent with a boiling point of at least 430 ° C.

are p- or m-acetoxybenzoic acid or a Mixture thereof with an alcohol in the presence of a condensation catalyst condenses to a polyester which has the general formula

Il

CH ₃ -C-

-OH

Attempts to make high molecular weight polyesters from hydroxybenzoic acids have shown face considerable difficulties. If hydroxybenzoic acids are heated with alcohols alone, the maximum effect is a little polymerization. A somewhat higher degree of polymerization can be achieved when using certain condensing agents. Polymers with low molecular weight, which contained only a few structural units in the molecular chain, were made Hydroxybenzoyl chlorides shown.

On the other hand, a high degree of polymerization can be achieved if acetoxyben zoic acids can be used. In this procedure

RO

hat In this formula, the bracketed part represents the periodically repeating hydroxybenzoyl structural unit, the p- or m-hydroxybenzoyl or - im same polyester molecule - can be both, depending on which monomer or monomers been used as starting material., ihd. Obviously, the success of this procedure is due to that Presence of the acetyl group instead of the hydroxyl group.

In the above-described hydroxybenzoyl polyester, the molecules end with on one side one acetoxy group and on the other side with a carboxyl group. Some of these polyesters do have certain useful properties, but also have serious disadvantages. A homopolymer prepared by the process described from p-acetoxybenzoic acid, for example, which is used as a p-hydroxybenzoyl polyester can be designated, the one on one side of the molecule with an acetoxy group and on the other side with one Carboxyl group ends, is only moderately heat resistant. It decomposes above 350 ° C, and compression molding this material is not due to its nature possible.

From US Pat. No. 3,039,994 are also Alkyl polyesters of hydroxy and acetoxybenzoic acids and processes for their preparation are known two these polyesters have a high melting point of about 450 ^° C., but their heat resistance leaves something to be desired.

The task was thus to provide hydroxy and acetoxybenzoyl polyesters which have high heat resistance and yet are malleable by pressing. There was also a procedure to specify the production of this polyester.

According to the invention, this object is achieved by the measures specified in claim 1. Advantageous developments of the invention and the method

so for producing the polyesters are given in the subclaims.

The molecule of the polyester according to the invention thus ends on one side with a hydroxyl or Acetoxy group and on the other side with one

Carbaryloxy group.

The principle of the manufacturing process and the nature of the polyester can be expressed by the following equation are shown, in general terms, the condensation of the monomer to the polyester illustrates;

-OR '

Π)

(II)

In this equation, the parenthesized part represents of the end product is the periodically recurring hydroxybenzoyl structural unit of the polyester. R represents a hydrogen atom or an acetyl group and R 'represents a phenyl, chlorophenyl or methylphenyl group. The hydroxy or acetoxy group are located on the ring in para- or meta-position to the carboxyl group, and a large number of the repeating structural units are a linear polyester linked, which ends at one end with a RO and at the other end with a COOR 'group

A general process for the preparation of the polyesters consists in that a monomer of the formula I given above or a mixture of such monomers is condensed in the liquid state at an elevated temperature. The condensation can be carried out in the absence of a solvent in the melt, but it is more advantageous to carry out it in a high-boiling solvent in an inert atmosphere and in the presence of a condensation catalyst at a temperature of at least 250 ^° C.

Extent of condensation and degree of polymerization in a certain period of time increase with increasing temperature. At room temperature there is no or only a small amount of polymerization instead. It is therefore advisable to start the condensation? as high as possible Temperatures to run. The highest applicable temperature depends in part on the boiling point or the Decomposition temperature of the monomer or monomers used. However, this temperature limit can to be exceeded to a degree, if one starts with a relatively low temperature and the temperature increases as it increases Condensation increases as the vapor pressure of the reaction mixture decreases

When a solvent is used, the highest condensation temperature is partly determined by the boiling point of the solvent The solvent must be a high boiling point, ie have such a high boiling point, that it at the temperature and ό under the conditions under which the condensation is carried out, not evaporated. Reactive solvents which interfere with the condensation cannot of course be used. Solvents with a boiling point of 250 ^° C. or above are particularly advantageous since they allow the condensation to be carried out at these temperatures under atmospheric pressure.

Numerous solvents have been found suitable. Examples include terphenyl, a eutectic mixture of 73.5% diphenyl oxide and 26 ^% diphenyl, a mixture of polychlorinated polyphenyls such as chlorinated diphenyls, polyphenyl ethers and other aromatic polyethers. Products of this type are commercially available under various trademarks; some of them have boiling points of 400 ^° C. and above.

All known transesterification catalysts can be used as condensation catalysts, for example Sodium alcoholates, titanium alcoholates, such as tetra-n-butyl orthotitanate, sodium titanium alcoholals, lithium hydroxide, Magnesium and p-toluenesulfonic acid.

After the process, polyesters can be produced with molecular weights of 25,000 and more to have. Molecular weights averaging 10,000 and more are very easy to achieve. In general the polyesters are characterized by an extraordinarily high level of heat resistance. The respective properties of each polyester depend on factors such as the molecular weight, the respective end groups and the type of bond between adjacent hydroxybenzoyl structural units, e.g. para or meta bond or both types of bond. Although certain applications of a given polyester also depend to some extent on its properties and its processability, the polyesters have a wide range of applications. For example, they can be used in the manufacture of polyester fibers, films and coatings of uncommon high temperature resistance can be used. They can also be used as binders for abrasive products to serve. Using the customary technical processes, they can be pressed into shaped bodies which have high flexural strengths.

A final theory to explain the excellent properties of the polyesters is not intended here be represented. But it seems that the present a carbaryloxy group instead of a carboxyl group improves the condensation reaction. More importantly seems to be that the aryl radical at the end of the The polyester molecule acts as a "blocking" group that prevents the breakdown of the molecule and it gives a higher heat resistance

The invention is explained in more detail by means of the following examples. Soferp, not otherwise indicated, are all Percentages by weight.

example 1

A mixture aiii 856 g phenyl-p-hydrobenzoat 0.015 g of tetra-n-butyl orthotitanate and 1,800 g of a Polychlorphenyls (bp. 360-370 "C) with constant stirring in an atmosphere of flowing nitrogen for 4 hours at 170 to 190 ⁰ C and then heated for 10 hours to 340 to 360 ° C. The mixture initially formed a homogeneous liquid. On further heating, the phenol was distilled off and the condensation set in and the polyester formed precipitated out. The reaction mixture was cooled to room temperature and the solvent was removed extracted with acetone the product was dried overnight in vacuo at 6O ⁰ C. the yield was 377 g of a polyester powder obtained which consists essentially of a p * Hydro. .ybenzoylpolyester consisted whose molecule on one side with a r hydroxyl group and at? the other end ended with a carbophenoxy group.

Eitle end group analysis indicated that the polyester had a molecular weight in excess of 10,000. The polyester was hydrolyzed to p-hydroxybenzoic acid and a small amount of phenol with strong alkali, thereby confirming the above structure. The polyester was found to be extremely heat-resistant. When heated in air at a temperature increase of 6 ° C / min, the total weight loss was less than 5% to 475 ° C less than 1% and up to 530 ⁰ C.

Test specimens were molded from the polyester powder at 440 ° C. with a pressure of 280 bar and tested according to ASTM methods. The following property values were found: Compressive strength (ASTM D-695) 26.5 kN / cm *; linear thermal expansion index (ASTM D-696) 5.1 x IO- ⁵ ; Flexural modulus (ASTM D-790) 824 kN / cm ² . Hardness and strength properties were retained to an excellent degree even at elevated temperatures.

The polyester appears to be predominantly more crystalline To be nature. It is true that up to temperatures of 525 ° C none of them could correspond to the crystalline state

sharp melting point can be found, but the polyester begins when exposed to heat and pressure to flow. This unique property appears to be a common characteristic of all hydroxybenzoyl polyesters to be in accordance with the invention. Although they do not melt at a temperature below their high decomposition temperature, they do flow when exposed to Heat and pressure. This surprising and very desirable behavior enables processing the polyester to use simple known processes. For example, plasma spraying, compression molding, Impact pressing and extruding at high speed for the production of foils and moldings with high temperature resistance can be used. Also other known processes, such as plasticizing with plasticizers, can be used.

Example 2

A mixture of 214 g of phenyl p-hydroxybenzoate, 0.022 g of tetra-n-butyl orthotitanate and 428 g of an aromatic polyether (bp> 440 ° C) as solvent was heated in an atmosphere of flowing nitrogen at a temperature of about 175 ° C the mixture turned into a homogeneous liquid. The temperature was increased to 300 to 320 ^° C. and kept in this range for 10 1/2 hours. Condensation occurred with removal of phenol by distillation, and the polyester formed precipitated. The reaction mixture was cooled to room temperature and extracted thoroughly with acetone to remove the solvent. The residue was dried in vacuo. 85.5 g of polyester were obtained, which essentially corresponded to the polyester prepared by the method of Example 1.

Example 3

A mixture of 3000 g of phenyl-p-hydroxybenzoate 0.15 g of tetra-n-butyl orthotitanate and 5,000 g of an aromatic Poiyäthers (Kp. About 440 ⁰ C) was heated with continuous stirring in an atmosphere of flowing nitrogen at a temperature of about 175 ^{At 3} C the mixture turned into a homogeneous liquid. The temperature was increased to 320 to 360 ° C. and held in this range for _{14 V for 2 hours.} Condensation occurred with removal of phenol by distillation, and the polyester formed precipitated. The mixture was cooled to room temperature and extracted with acetone to remove the solvent. The residue was dried in vacuo and gave 1325 g of polyester, which essentially corresponded to the polyester prepared by the method of Example 1.

Example 4

A mixture of 662 g of phenyl p-hydroxybenzoate and 0.030 g of tetra-n-butyl orthotitanate was stirred into an atmosphere of flowing nitrogen initially to a temperature of 93 ° C and then afterwards Table further heated:

60

65

total time temperature Course of reaction (H) (C) 0.0 93 0.5 185 The mixture is complete melted. 1.0 277 Phenol distilled from the Mixture from.

Total time, temperature, renessional flowC (h) (C)

U5 307 Product fails.

1.5 355 product solidifies,

Heating canceled.

The reaction mixture was cooled to room temperature and the solid mass, 360 g of which was obtained was crushed to a fine powder. The powder consisted essentially of a p-hydroxybenzoyl polyester, the molecule of which was on one side with one carbophenoxy group and terminated on the other side with a hydroxyl group. End group analysis indicated an average molecular weight of about 2000.

Mbar to 250 ⁰ C and '.'lmähliches raising the temperature during 3 Straden to 350 ⁰ C, the molecular weight was increased by heating the polyester under a vacuum of ISS.

As Example 4 shows, the condensation can also be carried out in the absence of a solvent in molten State of the starting material can be carried out by bringing the monomer to a temperature above Its melting point is heated, which is sufficient for condensation but below the boiling point of the monomer and also below the decomposition temperature of the polymer to the extent that the condensation progresses and the vapor pressure of the reaction mixture decreases the temperature gradually increased to increase the degree of polymerization. In general, it becomes beneficial be to continue the condensation until a highly viscous, but still flowable reaction product is formed that cools down to room temperature solidified The polyester mass obtained can, if desired, be ground to a powder. By Heating this powder can increase the molecular weight of the polyester.

Example 5

A mixture of 214 g of phenyl p-hydroxybetizoate and 428 g of an aromatic polyether (boiling point approx. 44O ⁰ Q as a solvent was used without the addition of a catalyst while stirring in an atmosphere of flowing nitrogen until a homogeneous liquid was formed and then further down to 327 C. The mixture was kept at this temperature for 7 hours. While phenol was distilled off, condensation occurred and the polyester formed precipitated Air-dried The yield was 109 g of polyester which was essentially the same as that of the polyester obtained by the method of Example 1.

Example 6

A mixture of 53.5 g of m-cresyl-p-hydroxybenzoate, 0.0219 g of tetra-n-butyl orthotitanate and 324 g of a high-boiling polychlorophenyl solvent was ^{heated to 280 to 300 °} C. for 7 hours in a nitrogen atmosphere with constant stirring . When heated to this temperature, the mixture turned into a homogeneous liquid. While distilling off

m-cresol condensation occurred and it fell in Hydroxybenzoyl polyester, whose molecule has a hydroxyl group on one side and a hydroxyl group on the other Side ended with a carb-m-cresoxy group. The mixture was cooled to room temperature and extracted with petroleum ether to remove the solvent. The residue was dried in vacuo and gave a yield of 21 g of polyester, the molecular weight of which based on an end group analysis was about 10,000.

Example 7

A mixture of 200 g of phenyl p-acetoxybenzoate and 400 g of an aromatic polyether as solvent was heated with constant stirring in an atmosphere of flowing nitrogen until a homogeneous liquid was formed. The temperature was then increased to 350 ^° C. and held at this level for 14 hours. With distilling off phenyl acetate, condensation occurred and the polyester formed precipitated. To remove the solvent, the precipitate was washed with acetone and dried in vacuo. The yield was 70 g of a polyester having substantially the same properties as the polyester obtained by following the procedure of Example 1. It was a p-hydroxybenzoyl polyester, the molecule of which ended with an acetoxy group on one side and a carbophenoxyl group on the other.

Example 8

From 36 g of p-acetoxybenzoic acid and 26 g of m-chlorophenol was in methylene chloride as a solvent and in the presence of 50 g of dicyclohexylcarbodiimide m-chlorophenyl p-acetoxybenzoate prepared.

A mixture of 11 g of m-chlorophenyl p-acetoxybenzoate and 100 g of an aromatic polyester as a solvent was added with stirring in a nitrogen atmosphere heated to 320-340 ° C and held at this temperature for 8 hours. While distilling off m-Chlorophenyl acetate condensation occurred and the polyester formed precipitated. The mixture was on Cooled room temperature and to remove the solvent repeatedly with a mixture of Washed trichlorethylene and petroleum ether. The product was then vacuumed overnight at 50 ° C dried The yield was 3.1 g of a polyester consisting essentially of a p-hydroxybenzoyl polyester consisted of whose molecule on one side with an acetoxy group and on the other side with a carbo-m-chlorophenoxy group.

In the preceding examples, the preparation of homopolymers is described for which as Starting material only one monomer is used. But it is also possible to have two or more monomers to use together. For example, polyesters that have both para and meta bonds in of the polymer chain, by using a para-bonded monomer and a monomer condensed together with a meta bond, as described in Example 9 below. The combination of two or more different monomers of the formula I given above is also possible such as the combination of diners of the type described below or of monomers and dimers.

Example 9

A mixture of 500 g of phenyl-p-hydroxybenzoate, 25 g of phenyl m-hydroxybenzoate, 0.074 g Lithiumhydro-% oxide and 1765 g of a Polychlorphenyls (bp. 360-370 ⁰ C) was heated in an atmosphere of flowing nitrogen with constant stirring until a homogeneous liquid was formed. The temperature was then increased to 300 to 320 ^° C. and at this level for 6 hours

kept in. Condensation occurred with removal of phenol by distillation, and the polyester formed precipitated. The mixture was cooled to room temperature and extracted with toluene to remove the solvent. The product became overnight at 150 ⁰ C in the vacuum

i "> dried. A yield of 224 g of a Polyester having a molecular weight of about 4,000 and consisting essentially of a hydroxybenzoyl polyester consisted of a molecule with a hydroxyl group on one side and a hydroxyl group on the other

. '"Carbophenoxy group and both para and meta bonds between the repeating hydroxybenzoyl structural units occurred in its polymer chain.
As noted, the presence of

2 '< Alkali or alkaline earth metals in the polyesters reduce their heat resistance. It is therefore generally expedient, when using alkali catalysts, such as lithium hydroxide, to leave a small amount of catalyst residue in the product

so could remove before processing the polyester. This can easily be done by the Polyester powder is washed with dilute hydrochloric acid or another mineral acid.

Copolymers containing various proportions of para-

Contain J5 and meta-hydroxybenzoyl structural units, Although the method of Example 9 can be manufactured, it is difficult to obtain a predetermined one To achieve arrangement of structural units. Depending on the para- and meta-monomers used and

• to various other factors it can happen that the para and meta structural units with others Structural units of the same type first form blocks and these then connect to form a polyester chain. On the other hand, the para and meta structural units can also combine in a random arrangement. However, some control over the arrangement of the para and meta bonds can be achieved by that one monomer is added to the other monomer in the course of the condensation to such an extent that

so depends on the respective reactivity of the monomers.

It seems that homopolymers of the meta type in contrast to the p-HydroxybenzoylpoIyestern im general melting points below the decomposition range. Hence are m-hydroxybenzoyl polyesters Particularly suitable for processing methods in which usually molten Polyester are needed. Furthermore, by introducing a few meta-bonds into a polyester, which is predominantly of the para type, can obtain a polyester which is not only excellent in heat resistance characteristic of the para-type polyesters, but also has a melting point has, which is below the high decomposition temperature. Such a polyester can be in molten Extrude the state and also process it according to other processes that start from a melt, for example into threads by melt spinning.

Example 10 describes a method that allow good control of the arrangement of para and meta bonds in the polyester molecule. at This process first creates a dimer from a para-monomer and a meta-monomer produced, which is then condensed to a polyester with alternately arranged para and meta bonds.

Preparation of the dimeric starting compound p-carbophenoxyphenyl-m-acetc / xybenzoate

From 2.14 g (0.01 mol) of phenyl p-hydroxybenzoate, 1.8 g (0.01 mol) of m-acetoxybenzoic acid and 85 ml of methyl chloride, a solution was prepared which, under Stirring 2.1 g (0.01 mol) of dicyclohexylcarbodiimide was added. The mixture was at for 16 hours Left to stand at room temperature; then the precipitated dicyclohexylurea was filtered off. The filtrate was evaporated until a paste remained which was triturated with 65 ml of methanol to obtain the dimeric ester p-carbophenoxyphenyl-m-acetoxybenzoate in solid form. The mixture was filtered and the product dried. A yield of 2.6 g was obtained. After recrystallization from methanol the product had a melting point of 104 - 106 ° C.

According to Schotten-Baumann, the same dimer can also be obtained from m-acetoxybenzoyl chloride and the sodium salt of phenyl p-hydroxybenzoate.

Example 10

A mixture of 180 g of dimeric ester meta.para p-Carbophenoxyphenyl-m-acetoxybenzoate, 0.022 g of tetra-n-butyl orthotitanate and 400 g of an aromatic polyether (Kp. About 440 ⁰ C) as a solvent was added with stirring in an atmosphere of flowing Nitrogen heated to 350 ° C for 3 hours. The mixture turned into a homogeneous liquid. The mixture was then held at a temperature of 350-360 ° C. for 4 hours. Condensation occurred with removal of phenyl acetate by distillation. The solution was cooled to room temperature and acetone was added. The precipitated polyester was filtered off, washed with acetone and dried in vacuo. A yield of 81 g of a polyester was obtained, the molecule of which consisted essentially of alternating p- and m-hydroxybenzoyl structural units and which ended with an acetoxy group on one side and a carbophenoxy group on the other. The copolymer had a softening point of about 220 ⁰ C. Upon heating in air at a temperature increase of 6 ° C / min to 400 ⁰ C, it shows no weight loss.

This is for the manufacture of fibers from the polyester placed in a metal vessel mm with a nozzle opening of 0.25 inner diameter is provided, the polyester is melted by heating to 300 ⁰ C, and from the melt threads are drawn off on a circumferential spindle.

While dimers of the type used in the procedure of Example 10, particularly for the production of polyesters with alternating para and meta bonds in the polymer chain are suitable, various other dimers of monomers of the general formula I are very general usable for the production of the polyesters and can, if desired, serve as starting materials instead of monomers.

There is a practical benefit to this 4 / experience

in that there is no need to use monomers which are free from small amounts of these dimers. For example, phenyl p-hydroxyl benzoate can be prepared from p-hydroxybenzoic acid and phenol by reaction of these components in the presence of POCb in a solvent such as toluene. Included small amounts of the dimer, trimer, tetramer, etc. can also arise. You can now use the dimer and the higher oligomers from the monomer

ίο disconnect and each component independently of the use another as a starting material for the manufacture of the polyester. However, such a separation is not necessarily required; one can also use the mixture to do essentially the same thing

Product to receive.

The high molecular weight polyester of the present invention can also be prepared by one in a first process stage by using lower condensation temperatures and / or kür lower reaction times a polyester with low Molecular weight produces and then the prepolymer obtained by heating in vacuo post-polymerized to a high molecular weight. The production of such a prepolymer or lower molecular polyester with a molecular weight between 500 and 2000 and its post-polymerization are described in Example 11 below.

Example 11

jo A mixture of 500 g phenyi-p-hydroxybenzoate, 0.0761 g of lithium hydroxide and 1000 g of a polychlorophenyl was with constant stirring in a The atmosphere of flowing nitrogen was heated until the mixture turned into a homogeneous liquid. then

j5, the temperature was increased and at 300 to 310 ⁰ C held for 3 hours at this level. Condensation occurred with removal of phenol by distillation, and the polyester formed precipitated. The mixture was cooled to room temperature and used to remove the solvent extracted with petroleum ether. The product was ^{dried at 60 °} C. in a vacuum. A yield of 344 g of a p-hydroxybenzoyl polyester was obtained, the molecule of which has a hydroxyl group on one side and a carbophenoxy group on the other side pe ended. The polyester was medium molecular weight in the order of 2000.

To remove the lithium hydroxide catalyst, the polyester powder was mixed with dilute hydrochloric acid washed. Then the polyester was taking 3 hours heated to 300 ° C. under a pressure of 13 mbar. The result was a polyester with a molecular weight of essentially> 10,000 and high heat resistance. When _{heated in air at 425 ° C. for 2/2} hours, the weight loss was only about 6%. The material can be ^{molded at 450 0} C with a pressure of about 1400 bar.

The production of the polyesters from a monomer of the formula I was described in the examples. Often is however, it is economically more advantageous to use the monomer from relatively inexpensive raw materials in to produce a solvent that is also suitable for the Condensation reaction is suitable and the condensation can be carried out without prior isolation of the monomer. For example, one can use p-hydroxybenzoic acid and phenyl acetate in a high-boiling aromatic polyether - preferably in the presence of a catalyst - ^{react at temperatures in the range from 180 to 220 °} C. and then add the product

condense the polyester, essentially following that described in the examples Procedure holds.

Particularly advantageous embodiments of the method are described in the examples, the. Of course, changes that are familiar to the person skilled in the art can be made for individual measures will. So instead of nitrogen, another inert gas, e.g. B. argon, to prevent a Oxidation of the reaction mixture can be used, ι ο The execution of the condensation in an inert gas atmosphere is beneficial, but not absolutely necessary; condensation can also occur in air be made without excessive oxidation. Likewise, the condensation under pressure or in ι> Vacuum. Also the separation of the polyester product from the solvent Extraction of the solvent with a more volatile solvent is only a particularly expedient one among other possible procedures. . '(>

The end group analysis mentioned in the preceding examples to determine the mean The molecular weight of the polyester was carried out in such a way that the polyester with sodium hydroxide was saponified, the end groups and structural units r> were separated and the respective proportions were determined. After the addition of a suitable reagent, the end groups became the structural units by colorimetry determined by gravimetry.

To compare the proposed according to the invention jo The following comparative tests were carried out between polyester and known hydroxybenzoyl polyesters.

Comparative example A.

According to the method of Example 1 of US Pat. No. 3,039,994, 30 g of the methyl «, tert of p-acetoxybenzoic acid were dissolved in 100 g of tri-n-butylamine, and the mixture was stirred at about 208 ^° C. for 16 hours (Temperature range 205 to 208 ° C) heated on the reflux condenser. During this time 4 g of distillate passed over, - »n which was collected and subjected to a chromatographic analysis. After the 16 hours had elapsed, the reaction mixture was cooled and filtered with suction. The residue on the filter was washed with 50 ml each of carbon tetrachloride, acetone, benzene and diethyl ether and then dried at 110 ° C. in vacuo. The product obtained with a yield of 1.5 g was subjected to a dynamic heat resistance test in which the temperature was increased by 5 ° C / min up to 400 ° C. At 225 ° C the weight loss was already 5%, at 325 ° C and 13% at 400 ⁰ C 22%. Gas chromatography of the distillate obtained from the reaction mixture showed that it contained 61.6% methyl acetate and no tributylamine; the rest had an unknown composition.

Comparative example B

The procedure of Example 4 of the referenced US patent was repeated. 30 g of ethyl ester of p-acetoxybenzoic acid were dissolved in 100 g of N, N-diethylaniline dissolved, which was free of N-monoethylaniline, and the reaction mixture was 17 hours at a temperature of about 210 ° C (temperature range 206-210 ⁰ C) reflux condenser heated, then cooled to room temperature. However, there was no precipitate.

Comparative Example C

A polyester according to the invention was prepared from phenyl p-acetoxybenzoate in an aromatic polyether by following the procedure of Example 1, a small amount of tetra-n-butyl orthotitanate being added as a catalyst and no catalyst being added at other times. The products were subjected to a dynamic heat resistance test in which the temperature to 400 ⁰ C at a rate of 6 ° C / min was increased. The weight loss up to 400 ^° C. was about 1% or less.

Comparative Example D.

Products of Examples I, 5, 7, 8 and 9 were tested for weight loss when heated in air to temperatures up to 650 and 700 ° C, the temperature being increased at a rate of about 5 ° C / min. Samples of about 4.5 g were placed on a support and heated. At temperatures up to 350 ^° C., there was no significant weight loss. In some samples, a noticeable weight loss was only found above 400 ° C.

In contrast, comparative tests with hydroxybenzoic acid ^{alkyl polyesters resulted in significant weight losses even at temperatures below 350 °} C., which were higher the higher the alkyl group of the ester.

Claims (3)

Patent claims: 1. Polyester with the general formula -OR ' wherein the parenthesized part is a structural unit with the oxy function on the ring in para- or meta-position to the carboxyl group and where a large number of these units are linked to form a linear polyester that has RO at one end and COOR 'ends at the other end, thereby characterized in that pure hydrogen atom or an acetyl group and R 'a phenyl, Mean chlorophenyl or methylphenyl group, and that the polyester is heat-resistant and through Pressing is malleable 2. Polyester according to claim 1, characterized in that the para and meta bonds in the Chain of the polyester essentially alternate one after the other. . 3. Process for the production of a polyester according to Claim 1. characterized in that at least one monomer of the general formula